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The quasibiennial oscillation (QBO) and semiannual oscillation (SAO) are the dominant modes of variability occuring in the tropical stratosphere. Previous studies have shown that the onset of the westerly phase of the QBO is seeded by the descending phase of the SAO . A recent study by Read and Castrejon-Pita (2012) showed evidence for phase-synchronisation of the QBO with the SAO .

Timeseries of monthly-mean zonal mean zonal wind are examined in model simulations submitted to the Coupled Model Intercomparison Project Phase 5 (CMIP5). Twenty-two models were examined for the presence of a
QBO in the equatorial stratosphere, of these only 3 displayed this behaviour. These models were then tested for phase synchronisation; only one model (MPI-ESM-MR) showed behaviour consistent with observations.